The present invention relates to a an organic solvent-soluble organopolysiloxane having a cage structure, and more particularly to an octasilsesquioxane-containing copolymer to its method of manufacture.
Because of their excellent heat resistance, electrical insulation, flame resistance, weatherproofness, and so forth, organopolysiloxanes have been utilized in the past as resist materials for semiconductors, insulator materials for motors, impregnated insulator materials for transformers, paints, primers, and so on (see "Silicone Handbook," edited by Kunio Ito, published in 1990 by Nikkan Kogyo Shinbunsha). Many different compositions and structures are known for organopolysiloxanes, and there is also a wide variety to their properties.
Still, there is a need for further improvements in the characteristics of these electrical and electronic materials. Examples of these characteristics include insulation, heat resistance, and durability.
The following art is known in regard to methods for manufacturing a copolymer in which a silsesquioxane is one of the copolymerization components.
Lichtenhan et al. have disclosed a method for manufacturing a copolymer in which a polyhedral oligomeric silsesquioxane is crosslinked (bonded) with a difunctional silane, siloxane, or organometal compound having a functional group such as an amine (J. D. Lichtenhan et al., U.S. Pat. No. 5,412,053; J. D. Lichtenhan et al., U.S. Pat. No. 5,589,562; and J. D. Lichtenhan et al., Chem. Mater., 1996, 8, 1250-1259). All of these disclose a method for manufacturing a copolymer in which a so-called incomplete cage structure where there is a defect in the cage of a silsesquioxane (a structure that is not a perfect octahedron, with part thereof missing) is bonded with a siloxane.
J. D. Lichtenhan et al. (Comments Inorg. Chem., 1995, 17, 115-130) have also disclosed a method for manufacturing a copolymer whose main chain is a silsesquioxane with an incomplete cage structure bonded with a siloxane or the like, and a method for manufacturing a copolymer in which a silsesquioxane with a cage structure is used as a pendant copolymerization component, and methacrylic acid is used as the copolymer main chain component.
Furthermore, J. D. Lichtenhan et al. (Macromolecules, 1993, 26, 2141-2142) have disclosed a method for manufacturing a silsesquioxane-siloxane copolymer by reacting bis(dimethylamino)silanes or the like with the OH groups bonded to the silicon atoms located in the corners of the incomplete cage structure of a silsesquioxane.
Methods for manufacturing a copolymer by reacting a silsesquioxane having an incomplete cage structure with another compound have been disclosed in J. D. Lichtenhan et al. U.S. Pat. No. 5,484,867 and by Sellinger et al. in Macromolecules, 1996, 29, pp. 2327-2330.
U.S. Pat. No. 5,484,867 discloses a method for manufacturing a graft copolymer having a pendent silsesquioxane in which a vinyl group-containing compound is bonded in the corner of a silsesquioxane with an incomplete cage structure, and this compound is graft polymerized to another copolymer via the above-mentioned vinyl group, as well as a method for manufacturing a silsesquioxane-added ABA-type block copolymer obtained by the reaction of the vinyl groups of the above-mentioned vinyl group-containing silsesquioxane compound and a copolymer having vinyl groups at both ends. There is general mention that variable factors such as substituents affect the thermal characteristics, solubility, and so forth of the copolymer that is obtained.
The above-mentioned article by Sellinger et al., Macromolecules, 1996, 29, pp. 2327-2330, discusses a method for manufacturing a cage-type silsesquioxane in which methacrylate groups have been introduced at a plurality of the cage corners by subjecting propargyl methacrylate and a cage structure silsesquioxane to hydrosilylation, and it is stated that the product obtained by this method is soluble in organic solvents.
Nevertheless, the above-mentioned publications do not discuss a method for manufacturing a soluble copolymer consisting of one or more linked hydrogenated octasilsesquioxanes by reacting and bonding the hydrogen of hydrogenated octasilsesquioxane with at least one of the vinyl groups of a compound having vinyl groups at both ends through hydrosilylation.
Hoebbel et al. (J. Non-Crystalline Solids, 176 (1994), 179-188)) have disclosed a method for manufacturing a complete cage-type silsesquioxane compound in which vinyl groups are bonded at a plurality of the cage corners via Si--O-- bonds, and have reported that the copolymer obtained from this compound is a transparent gel (that is, the copolymer thus obtained is insoluble).
Furthermore, 1. Hasegawa (J. of Sol-Gel Sci. and Technol. (1995), 5 (2), 93-100) has disclosed a method for manufacturing a compound in which the cage structure of silsesquioxane is not destroyed, and is merely bonded with dimethylsilyl groups.
None of the cited literature has disclosed a method for manufacturing a copolymer that is soluble in organic solvents and has hydrogenated octasilsesquioxane on its main chain by reacting a hydrogenated octasilsesquioxane having a cage structure (that is, hydrogenated octasilsesquioxane) and a compound having vinyl groups at both ends by a hydrosilylation reaction.
There has been a need for a copolymer that has excellent electrical insulation properties and whose heat resistance, weatherproofness, oxidation resistance, and so forth are superior to those obtained with the above-mentioned prior art. It is an object of the present invention to provide a method for manufacturing a material that meets the above need, namely, an organic solvent-soluble copolymer (hereinafter referred to as the "present copolymer", in which hydrogenated octasilsesquioxane and a compound having vinyl groups at both ends are allowed to react by hydrosilylation. Here, the compound having vinyl groups at both ends is one of the monomer components that constitute the copolymer, but in the sense that it has an action of bonding the hydrogenated octasilsesquioxane, it can also be called a crosslinking agent.